I have done a bunch of work on the engine / transmission, or, I have had work done on engine and transmission. It's no longer leaving puddles of oil from engine, transmission and Diff, but i am finding a small film of oil on the oil pan after a 30-40 minute drive. Still no drips on the garage floor, but a small film of oil. I had been a land rover owner for over 25 years, before buying my 1954 Chevy 3100. And after years of spending money fixing oil leaks, and finally being told, "Kevin, it's ok, they are going to leak a little bit. Not worth trying to solve it" Should I say good enough on the oil leak of my 235 engine, or should I pull bits apart and try to fix every small dribble?
34 Years. Now with a '61 261, 848 head, Rochester Monojet carb, SM420 4-speed, 4.10 rear, dual reservoir MC, Bendix up front, 235/85R16 tires, 12-volt w/alternator, electric wipers and a modern radio in the glove box.
You can make the 235 oil tight up to a point. That "point" is the rear main seal. I only know of one way to make the rear main oil tight and that is to polish the seal surface well and have the rear part of the block machined to accept a one-piece lip seal.
~ Jon 1952 1/2 ton with 1959 235 | T5 with 3.07 rear end
On road draft tube equipped engines that just have a film of oil like yours a pcv valve will usually keep everything clean. They were offered from the factory for big truck applications but are easy to make. There are numerous "how to" articles on this so read up before starting. Done wrong you will have a mosquito fogger.
Show me an old Chevy six that doesn't leak some oil and I'll show you an old Chevy six that is out of oil. Minimizing leaks is good and achievable. Trying to stop all leaks is folly. As noted above the film of oil on the pan is likely coming from the road draft tube. Engines of that era were not designed to be leak free because the environmental concerns were not present. An old Chevy six that doesn't mark her parking spot is almost unicorn rare.
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I don't know how it goes for that specific engine, but I can say that, in my experience, those blue rubber gaskets are like the Messiah for fixing oil and tranny fluid leaks. I had a 327 on my Chevelle that I was sure liked to drip at the timing cover just to make my BP go up, and it had the old school gaskets on it.
The 350 in my Panel Truck has the blue rubber gasket, and the only leak I noticed was right after I reassembled it and fired it up for the first time. I cranked down that one pan bolt, and no more leak. May be worth seeing if they make those gaskets for the 235.
Of course, by posting this response, I've probably now jinxed myself with new leaks.
Thanks for all the feedback. I Drove the furthest I had since owning the vehicle to a Cars and Coffee event. about an hour each way. After the event, I pulled the truck into the garage and now will monitor the floor under the truck for any dripping. No drips since Sunday AM, so I'm feeling pretty good.
Old Harleys, Detroit Diesels, and stovebolts "mark their territory". Unless it's leaving puddles, chances are it's about as clean as it's going to get. Give it a good pressure wash at the local coin car wash on occasion, so the seepage can be monitored and dealt with if it starts getting out of hand. In general, "the more you run it, the less it's going to leak"- - - -especially if you're dealing with the old style rope rear oil seal. That will give you a really good excuse to get out and drive it frequently! Jerry
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